When setting "GRUB_GFXPAYLOAD_LINUX=1920x1080" (which is my screenresolution) in /etc/default/grub and running "update-grub" the password prompt appears.
Trusty is not affected by this bug on my system, only utopic. I tried trusty and upgraded the kernel to the utopic version, but it still worked.
I played around and found the following:
When setting "GRUB_GFXPAYLOA D_LINUX= 1920x1080" (which is my screenresolution) in /etc/default/grub and running "update-grub" the password prompt appears.
Trusty is not affected by this bug on my system, only utopic. I tried trusty and upgraded the kernel to the utopic version, but it still worked.